Solid substances or foams are often required to have special quality or strength properties. Additives are introduced into the reaction mixtures from which these materials are to be formed in order to improve the properties or lower the cost of these materials. In the first case, the additives are pulverulent, fibrous, platelet or granular reinforcing substances, such as, in particular, glass fibers, mica or barium sulfate. In the second case, the substances are fillers which are inferior in quality and less expensive than the reaction components, such as chalk powder, sawdust or ground foam waste.
Various proposals have been made for constructing the apparatus in order that the additives may be directly introduced into the reaction mixture or mixed with one of the reactants. Unfortunately, the manner in which these additives are introduced in the prior proposals has created inaccurate additive dosages and has allowed air to be introduced into the component with the additive, the air having a deleterious effect on the quality of the end product.
In order to ensure exact ratios of additive to component, the practitioner has been forced to first mix the additives with at least one of the reaction components in a stirrer vessel and operate batchwise. This method, however, produces a considerable amount of dust which is inconvenient for the operators and, in some cases, even substantially falsifies the proportions of the doses. There is a further difficulty with particular reinforcing additives, such as short fibers, in that when these particular substances are further size-reduced during the mixing process, their reinforcing properties are changed and the apparatus is subjected to greater wear. Under all these conditions, it is presumed that the additives should be homogeneously distributed in the reaction components within as short a stirring time as possible.
It is an object of the present invention to provide a process with which pulverulent and other small-particled additives may be added in the exact proportions to at least one of the reaction components without loss and without producing dust. A further object is to provide a process to mix pulverulent additives within a short time into a reaction component which may then be degassed.